Insertion of CO2, CS2, and COS into iron(II)-hydride bonds.

Abstract

The reactions between cis-Fe(dmpe)2H2 (dmpe = Me2PCH2CH2PMe2) (1) or cis-Fe(PP3)H2 (PP3 = P(CH2CH2PMe2)3) (2) and carbon dioxide (CO2), carbon disulfide (CS2), and carbonyl sulfide (COS) are investigated. At 300 K, additions of CO2 (1 atm), CS2 (2 equiv), and COS (1 atm) to 1 result in the formation of a stable transformato hydride, trans-Fe(dmpe)2(OCHO)H (3a), a trans-dithioformato hydride, trans-Fe(dmpe)2(SCHS)H (4a), and a trans-thioformato hydride, trans-Fe(dmpe)2(SCHO)H (5a), respectively. When CS2 and COS are added to cis-Fe(dmpe)2H2 at 195 K, a cis-dithioformato hydride, 4b, and a cis-thioformato hydride, 5b, respectively, are observed as the initially formed products, but there is no evidence of the corresponding cis-formato hydride upon addition of CO2 to cis-Fe(dmpe)2H2. Additions of excess CO2, CS2, and COS to 1 at lower temperatures (195-240 K) result in the formation of a trans-bis(formate), trans-Fe(dmpe)2(OCHO)2 (3b), a trans-bis(dithioformate), trans-Fe(dmpe)2(SCHS)2 (4c), and a cis-bis(thioformate), cis-Fe(dmpe)2(SCHO)2 (5c), respectively. trans-Fe(dmpe)2(SCHO)2 (5d) is prepared by the addition of excess COS at 300 K. Additions of CO2 (1 atm), CS2 (0.75 equiv), and COS (1 atm) to 2 at 300 K result in the formation of a thermally stable, geometrically constrained cis-formato hydride, cis-Fe(PP3)(OCHO)H (6a), a cis-dithioformato hydride, cis-Fe(PP3)(SCHS)H (7a), and a cis-thioformato hydride, cis-Fe(PP3)(SCHO)H (8a), respectively. Additions of excess CO2 and COS to 2 yield a cis-bis(formate), cis-Fe(PP3)(OCHO)2 (6b), and a thermally stable cis-bis(thioformate), cis-Fe(PP3)(SCHO)2 (8b), respectively. All complexes are characterized by multinuclear NMR spectroscopy, with IR spectroscopy and elemental analyses confirming structures of thermally stable complexes where possible. Complexes 3b and 5a are also characterized by X-ray crystallography.